Moisture sensor including volume sensing

ABSTRACT

A moisture sensor includes a circuit board and a plurality of circuits monitoring a plurality of moisture probes, wherein at least two sets of a plurality of probes are on the bottom of the sensor, one set in direct contact with the floor, a second set separated from the floor; a set of conductive pins that enable the body of the circuit board to be spaced from the floor to help any moisture accumulation beneath the sensor to evaporate, preventing mold growth; two sets of a plurality of probes along the edge of the sensor, such that when the sensor is installed edge on, these edge sensors will be in direct contact with the floor. The sensor transmits data periodically when sensed resistance is below a predetermined value.

CROSS-REFERENCE TO RELATED APPLICATIONS

U.S. Provisional patent application Nos. 62/622,552, filed 26 Jan. 2018,and 62/535,078, filed 20 Jul. 2017, are incorporated herein byreference. Priority of these applications is hereby claimed.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable

REFERENCE TO A “MICROFICHE APPENDIX”

Not applicable

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to wireless moisture sensors that areuseful tools to detect and alert automated systems of destructive waterleaks from pressurized water sources, drain leaks, roof leaks, etc. inresidential and commercial spaces.

2. General Background

Wireless moisture sensors are useful tools to detect and alert automatedsystems of destructive water leaks from pressurized water sources, drainleaks, roof leaks, etc. in residential, industrial, medical, andcommercial spaces, for example.

There are a number of existing leak detectors (both wired and wireless)that essentially depend on monitoring the electrical conductivitybetween one or more probes either in direct contact with the floor, or asmall fixed distance from the floor (typically about 1/32″ to 1/16″).

Current wireless sensors are on the order of ½″ to 1″ in height and witha single moisture sensing circuit monitoring a plurality of moistureprobes. A problem to be overcome with any moisture sensor is that somesurfaces can be damp under normal circumstances where there is no leak.The moisture typically is the result of warm moist air in contact with arelatively cool surface, such as cool tile in the bathroom after a hotshower. Further, some surfaces are simply conductive, such as a metalcatch pan under an HVAC unit. Currently, some moisture sensors employprobes in direct contact with the floor, or probes separated by a gap.It is also worth noting, all the sensors known to the present inventorswhich are currently available employ probes only on the bottom of thesensor.

Currently all moisture sensors known to the inventors report either thepresence or absence of moisture in a binary fashion (i.e. “moisturealarm” or “moisture clear”) based on a predetermined resistancethreshold between moisture probes, based on the fact that water isalmost invariably a good conductor.

Some sensors employ a basic tilt or vibration sensor to detecttampering, but not an accelerometer. In other words, they can detectmovement but not the sensor's physical orientation.

A problem with prior art moisture sensors is that moisture trappedbeneath the sensor takes an extended length of time to dry, on the orderof days. This is in large part due to the very low surface to volumeratio of the trapped water. Only the water exposed around the perimeterof the sensor can evaporate.

BLINK VIDEO HOME SECURITY (https://blinkforhome.com/) sells indoor andoutdoor motion-activated cameras which detect temperature and recordvideo and sound. The outdoor cameras are advertised to be weatherproof.The outdoor cameras have IR illumination with user-set intensity. Thesensitivity of the motion detector is also adjustable, as is the lengthof the recording and the frequency of recording when motion continues tobe detected.

The following patent documents are incorporated herein by reference:

-   -   U.S. Pat. Nos. 4,696,796; 4,801,865; 4,920,451; 6,700,395;        6,756,793; 7,231,727; 7,528,711; 7,719,432; 8,281,645;        9,780,554; 9,226,076;    -   U.S. Patent Application No. 20170030851A1;    -   other patent documents: DE10,249,370; EP0178071B1; and        WO1999026499A2.

BRIEF SUMMARY OF THE INVENTION

The apparatus of the present invention solves the problems confronted inthe art in a simple and straightforward manner.

What is provided, among other inventions, is a moisture sensor that caninclude a plurality of circuits monitoring a plurality of probes, someof which are in direct contact with the floor, others spaced from thefloor. Further, the plurality of probes being monitored by a pluralityof circuits can preferably detect, and therefore report, the presence ofmoisture on precisely and only those probes in contact with moisture.Further, the present invention preferably provides for the ability tomeasure and report the level of electrical resistance presented by themoisture impinging on the probes, precisely and only the impingedprobes, and to therefor report a relative level of moisture, or“wetness” presented to each of a subset of the plurality of probes. Thissensing circuit functionally, and herein is also referred to asohmmeter.

In addition to sensing moisture by electrical conductivity, theinvention also provides a unique physical embodiment of a moisturesensor that detects the presence of moisture by capacitive proximity aswater has a much larger dielectric constant than other substances foundin a residence or business.

Preferably, also provided is a unique physical embodiment of a moisturesensor employing the circuit board itself as part of the electronicenclosure to reduce cost.

Preferably, also provided is a unique method of employing anaccelerometer to both detect and report tampering with the sensor, andto also detect the sensor's physical orientation.

Preferably, also provided is a unique physical embodiment of a moisturesensor that includes a temperature sensor, to detect the likely suddenchange in sensor temperature from ambient room temperature to thetemperature of the water from a leak. This allows further correlation ofsudden leak detections to help filter out false alarms.

The prior art known to the inventors employs probes either in contactwith the surface, or not in contact with the surface, typically around1/16″ above the surface. Both the contact and non-contact designs areproblematic and therefore not perfect for all situations. The currentinvention provides a solution to the problems of the prior art byproviding a plurality of moisture probes, a subset of which are incontact with the surface and a further subset separated from the surfaceby typically around 1/16″. Thus, one sensor can monitor both the surfacefor the presence of latent moisture, such as for example damp wood, andsimultaneously monitor for only significant accumulations of moisturestanding on the surface, such as for example water leaking onto a tilefloor.

The probes can be implemented as conductive regions and conductive pinsor feet on a printed circuit board that are affixed to the bottom of thesensor enclosure. The printed circuit board preferably serves both asthe moisture probe and the bottom of the enclosure, thus reducingmanufacturing costs. There is not a necessity for a molded bottom, thusthe height of the overall enclosure can be lower.

The arrangement of the probes around the perimeter of the sensor, asopposed to the bottom only, enables the sensor to work in a variety ofdifferent orientations (e.g., inclined or generally horizontal).

The probe can provide a circuit board that works in a variety oforientations. In a flat generally horizontal orientation, conductivepins are in direct contact with the floor and detect any moisture, whilethe conductive regions on the bottom of the circuit board also detectleaks, but are immune to surface condensation. The conductive pins alsoraise the sensor bottom from the floor thus enabling moisture toevaporate (as opposed to mounting the circuit board directly to thefloor). In an edge, vertical orientation, perimeter probes becomecontact probes, while the conductive regions (by virtue of the fact theyare terminated preferably about 1/16″ from the edge) also detect leaks,but are immune to surface condensation.

A circuit board can be affixed to the enclosure (e.g., plastic) forexample by means of conductive screws that also serve as moistureprobes, along with adhesive water-proof strips and/or O-rings and/orseals so that the internal battery and internal electronic circuit areprotected from water impinging on the sensor during a leak, and toprotect from condensation from atmospheric moisture.

A moisture sensor measures the resistance between probes to determinethe presence of moisture. To do so, the sensing circuit measures howmuch current is able to flow between the probes. With a battery-poweredsensor it is preferable to measure the conductivity between probes usinga minimum amount of current. The microcontroller uses an additionalamount of energy as it typically wakes up periodically to measure thiscurrent flow.

The present invention preferably employs a small capacitor on two of thefour probes, with the remaining two probes connected to themicrocontroller and to ground through a very large resistance. Themicrocontroller preferably periodically charges those capacitors andonce charged, the microcontroller preferably goes into a sleep mode,preferably waking up only when the charge on one of the capacitors hasdrained below a detection threshold. This arrangement allows themicrocontroller to sleep for extended periods of time (a minute orlonger) yet be able to respond virtually instantly to a leak event.

Preferably, via the remaining two remaining probes, the microcontrollercan detect which two of the four probes was involved in the leak. Therate at which the probe capacitors discharge gives an indication of theresistance between the probes.

In the present invention, measurement of a range of values of resistancepreferably occurs, rather than just a binary wet/dry indication of manyprior art sensors. Also, multiple probes on different areas of thesensors allow more and better information to be obtained via severalohmmeters. The ability to conduct capacitive sensing makes sensors ofembodiments of the present invention desirable. Conductive probes thatcan pierce gypsum board allow sensors of embodiments of the presentinvention desirable in that the moisture in the gypsum board can giveinformation about leaks in a building. It is believed that in thepresent invention a battery could last 10-15 years (or longer). Thebattery shelf life may be the limiting factor.

Advantageous features of the present invention include:

1. a plurality of analog-reporting ohmmeters and capacitive sensors;

2. the resistive and capacitive sensors are especially capable atreading small variations in adjacent surface moisture content becausethe conductivity and capacitance of porous surfaces increases inproportion to moisture content. And most building material surfaces areporous (tile, wood, concrete, etc.)

3. the capacitive sensor is more immune to false alarms than resistivesensors because it can discern the actual volume of water, whereasresistive sensors can be falsely triggered by lint/dirt/cleaningproducts etc. spanning the relatively short distance between probes wheninfused with a very small amount of water, and can be triggered byinnately conductive surfaces such as metal;

4. the capacitive sensor is immune to corrosive chemicals because nometallic conductive probes or regions of the circuit must be exposed, asopposed to resistance-measuring moisture sensors;

5. sensitivity of the capacitive sensor is greatly increased withoutincreased cost by utilizing the circuit board as the bottom enclosure;

6. the small size of the sensor design (preferably smaller than 2.3″ Linches by 2.5″ W inches by 0.5″ H inches);

7. the under-sensor spacer that speeds drying, allowing the sensor toremain in place without needing to be manually moved to dry the floor;

8 two or more separate under-the-sensor spacers made of a conductivematerial placed in intimate contact with conductive regions under thesensor (thus each spacer becoming part of a plurality of electricalcircuits), and also in contact with the adjacent surface (and furtherbeing optionally affixed to the surface), enabling the sensor, throughthe intervening spacers (made of for example carbon impregnated rubber),to measure surface resistance using materials otherwise impervious tocorrosive chemicals, while protecting the metallic conductive region ofthe sensing circuit;

9 a variation of the resistive sensor with penetrating probes thatmeasures the moisture in porous materials like sheetrock or wood (suchas pine, cedar, cypress, oak and engineered wood), enabling a smallsensor to detect moisture in the space behind the porous material thatis even some distance away (as far away as for example twenty feet), asthe unwanted moisture results in much higher humidity in the space, andwill likely cause a large area of porous material to become moreconductive; and

10. preferably relative humidity, ambient light, ambient noise, waterflow, surface moisture, temperature, etc. readings from proximatelyco-located sensors and distant sensors in similar locations (aparticular bathroom compared to others in the same unit space, and toother unit spaces) can be compared/correlated/statistically analyzed toreduce false alarms (such as humid bathroom floors, shower curtainspills, etc.).

Processing the Data

The internal processor and transmitter preferably relay the currentstate of the resistance between the moisture probes, as well as whichprobes are involved. Reporting the resistance between the probes and/orcapacitance, rather than a binary moisture/no-moisture condition,enables the sensor to relay the fact that a moisture condition exists,but is either advancing or receding. This feature allows the sensor incertain situations to deduce that the leak has stopped even though theprobes are still in contact with a moist but drying surface. Thisfeature also allows the nature of the leak to be characterized, such aswhether the leak presented suddenly or slowly, in many cases making itpossible to pinpoint much more accurately when the leaking conditionbegan. This also allows the sensor to be permanently attached to asurface, or to be deployed in locations that are difficult to access,without the need to dry the surface after a leak event.

Because the sensor may be permanently attached to the floor (forsecurity, or to perpetually ensure optimum location at time ofinstallation, etc.) in areas where the floor must be cleaned (such as bymopping), it is possible for a damp mop to temporarily touch themoisture probes, creating a false leak alarm. Because a plurality ofcircuits will be monitoring a plurality of probes, it is possible tofilter out this false alarm condition by requiring a combination ofprobes to detect moisture, but in a pattern not consistent with a moptouching the sensor.

The sensor preferably employs an accelerometer that detects bothmovement and the orientation of the sensor. It preferably also relaysthe sensor's orientation via readings from the accelerometer. Other dataare preferably also relayed, including the current battery state, etc.The accelerometer preferably reports the current orientation of thesensor (e.g., flat, upright, etc.) accurate to at least 2 mg (milligravity) in the x-, y- and z-axes.

Further, the sensor preferably sends periodic transmissions so that thereceiving processor can verify the status of the sensor, as well as theradio signal strength. During the periodic update, any changes in thestate of the sensor are preferably also transmitted, but only if changesoccurred. By omitting redundant data, the battery power can beconserved.

The sensor of the present invention can advantageously be used with theleak detection system disclosed in International Publication Number WO2017/019801 A1, published 2 Feb. 2017, assigned to ENCO ELECTRONICSYSTEMS, LLC, and incorporated herein by reference.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

For a further understanding of the nature, objects, and advantages ofthe present invention, reference should be had to the following detaileddescription, read in conjunction with the following drawings, whereinlike reference numerals denote like elements and wherein:

FIG. 1 is a perspective view of a first embodiment of the sensorapparatus of the present invention;

FIG. 2 is a bottom view of a first embodiment of the sensor apparatus ofthe present invention;

FIG. 3 is an exploded view of a first embodiment of the sensor apparatusof the present invention;

FIGS. 4-7B are circuit diagrams of a preferred embodiment of theapparatus of the present invention to detect moisture accumulation onand within a surface by measured resistance between a plurality ofprobes;

FIGS. 8-11B are circuit diagrams of a preferred embodiment of theapparatus of the present invention to detect moisture on and within asurface by measured capacitance between a plurality of probes;

FIGS. 12-14B are circuit diagrams of a preferred embodiment of theapparatus of the present invention to detect moisture in a substrate bymeasured resistance between a plurality of probes;

FIG. 15 is a top view of an evaporative aid for promoting betterevaporation;

FIG. 16 is a perspective view of a preferred embodiment of the presentinvention with an evaporative aid situated on its bottom and on top ofthe floor, with the arrows depicting the moisture exiting;

FIG. 17 is a top view of a preferred embodiment of the present inventionwith an evaporative aid;

FIG. 18 is a perspective view of a preferred embodiment of the presentinvention with an electrically conductive evaporative aid;

FIG. 19 is a bottom perspective view of a preferred embodiment of thepresent invention with an electrically conductive evaporative aid;

FIG. 20 is a top perspective view of an electrically conductiveevaporative aid showing the contacts of a conductive spacer;

FIG. 21 shows a horizontal orientation and vertical orientation of apreferred embodiment of the present invention;

FIG. 22 shows an interior of the enclosure of a preferred embodiment ofthe present invention;

FIG. 23 shows an exterior of a bottom panel of an enclosure of apreferred embodiment of the present invention;

FIG. 24 shows a classic resistor-capacitor discharge circuit utilized bya preferred embodiment of the present invention;

FIG. 25 is a schematic view showing components of the present invention;

FIG. 26 is a schematic view showing components of the present invention;

FIG. 27 shows a bottom enclosure of a preferred embodiment of thepresent invention;

FIG. 28 is a perspective view of a bottom enclosure of a preferredembodiment of the apparatus of the present invention to detect moistureon and within a surface by measured capacitance between a plurality ofprobes;

FIG. 29-31 show how the electric field generated by the capacitivestructure can be steered by changing the polarity of a plurality ofconductors;

FIG. 32 is a view of a bottom enclosure of a preferred embodiment of theapparatus of the present invention to detect moisture on and within asurface by measured capacitance between a plurality of probes;

FIG. 33 is a top view of a preferred embodiment of the apparatus of thepresent invention wherein the detection of water is signaled by one ormore LEDs;

FIG. 34 is a perspective view of a preferred embodiment of the apparatusof the present invention wherein the detection of water is signaled byone or more LEDs;

FIG. 35 shows capacitive circuitry and methods of using the capacitivecircuitry.

DETAILED DESCRIPTION OF THE INVENTION

Moisture sensor apparatus 10 measures moisture by resistance and is seenin FIGS. 1-3, 22-23. FIGS. 4-7 are circuit diagrams of a preferredembodiment of the apparatus of the present invention to detect moistureaccumulation on and within a surface by measured resistance between aplurality of probes. The circuit diagram depicted in FIG. 5 is shown ingreater detail in FIGS. 5A and 5B. The circuit diagram depicted in FIG.6 is shown in greater detail in FIGS. 6A and 6B. The circuit diagramdepicted in FIG. 7 is shown in greater detail in FIGS. 7A and 7B. FIGS.8-11 are circuit diagrams of a preferred embodiment of the apparatus ofthe present invention to detect moisture on and within a surface bymeasured capacitance between a plurality of probes. The circuit diagramdepicted in FIG. 9 is shown in greater detail in FIGS. 9A and 9B. Thecircuit diagram depicted in FIG. 11 is shown in greater detail in FIGS.11A and 11B. A moisture sensor apparatus 110 which detects moisture bymeasured capacitance is seen in FIGS. 27-30. FIGS. 12-14 are circuitdiagrams of a preferred embodiment of the apparatus of the presentinvention to detect moisture in a substrate by measured resistancebetween a plurality of probes. The circuit diagram depicted in FIG. 12is shown in greater detail in FIGS. 12A and 12B, and the circuit diagramdepicted in FIG. 14 is shown in greater detail in FIGS. 14A and 14B.FIGS. 15-17 demonstrate an evaporation aid 30 of a preferred embodimentof the apparatus of the present invention. The evaporative aid can alsobe electrically conductive and subdivided into individual circuits 42,being electrically connected to the sensing circuit by any number ofmeans including exposed circuit board traces and by means of conductiveadhesives, or by screws, etc. An electrically conductive evaporative aid41, also referred herein as a conductive spacer, is shown in FIGS.18-20. An electrically conductive evaporative aid 41 could take theplace of a plain evaporative aid 30 shown in FIGS. 15-17

The sensing apparatus 10 of the present invention includes an enclosure11 (made of, e.g., plastic) having a bottom panel 12, a top section 18and an interior for holding components such as electronics andbatteries. Bottom panel 12 has lower surface 16, upper surface 21 andperiphery 22. Bottom panel 12 preferably is a printed circuit board andcan be affixed to enclosure 11 interior with conductive screws 13 thatalso serve as moisture probes, along with adhesive water proof stripsand/or O-rings and/or seals as examples (not shown).

As shown in FIG. 22, enclosure 11 contains an internal battery 34, aprocessor or microprocessor or computer, and a transmitter. As enclosure11 is preferably waterproof, these components are protected from waterimpingement during a leak or spill. The enclosure 11 is thus preferablywater-tight to protect from condensation, atmospheric moisture inaddition to leaking or spill from nearby sources such as a sink, shower,appliance, toilet or the like. Optionally, the circuit board can beselectively conformally coated 15 (avoiding coating those areas thatmust be exposed, such as resistance measuring probes or exposed regionsof the circuit) (see FIG. 3).

A number of probes 37 are provided adjacent enclosure 11. Some of theseprobes can sense a spill or leakage when in a horizontal or generallyhorizontal position or orientation (see the leftmost moisture sensorapparatus in FIG. 21). Some of these probes can sense a spill or leakagewhen in an inclined, edge, or vertical orientation (see the rightmostmoisture sensor apparatus 10 in FIG. 21.

One or more contact probes 13 extend from lower surface 16 of bottompanel 12 (see FIGS. 1-3). Probes 20 can also be provided on enclosure11. The lower surface 16 also includes contacts 37 for sensing anaccumulation of moisture, and located on the lower surface 16 such thatthey are equidistant from the adjacent surface (typically the floor)when the apparatus is lying flat on the floor, or vertically.

Unique Moisture Probe

The moisture sensor of the present invention preferably includes aplurality of circuits 38 monitoring a plurality of probes 13, 20, 37some of which (13) are in direct contact with the floor, while othersare spaced from the floor (20, 37), as shown in FIGS. 1, 3. The probesare preferably implemented as conductive regions and conductive pins orfeet on a printed circuit board 39 that is affixed to the bottom of thesensor enclosure. The bottom 12 of the sensor enclosure serves both asthe moisture probe and the bottom of the enclosure. As a result,manufacturing costs are reduced, and without the necessity for a moldedbottom, the height of the overall enclosure is lowered.

The arrangement of the probes 37 around the perimeter of the sensor (seeFIG. 3), as opposed to the bottom only, enables the sensor to work in avariety of orientations as shown in FIG. 21.

The probe circuit board works in a variety of orientations, butprimarily:

In a flat horizontal orientation (see the leftmost moisture sensorapparatus 10 in FIG. 21; see also FIG. 1), the conductive pins 13 (seenin FIGS. 1-3) are in direct contact with the floor and detect anymoisture, while the conductive regions 20 on the bottom of the circuitboard also detect leaks, but are immune to surface condensation. Theconductive pins 13 also raise the sensor bottom 12 from the floor 27enabling moisture to evaporate (as opposed to mounting the circuit boarddirectly to the floor) (as seen in FIG. 1.

In an edge, vertical orientation (see the rightmost moisture sensorapparatus 10 in FIG. 21), the perimeter probes 37 (see FIG. 3) becomecontact probes, while the conductive regions 20 (by virtue of the factthey are terminated preferably about 1/16″ from the edge) also detectleaks, but are immune to surface condensation.

The circuit board is preferably affixed to the plastic enclosure bymeans of conductive screws that also serve as moisture probes, alongwith adhesive water proof strips and/or O-rings and/or seals and/orselective conformal coating so that the internal battery, processor andtransmitter are protected from water impinging on the sensor during aleak, and to protect from condensation from atmospheric moisture.

Unique Resistance Sensing Circuit

A moisture sensor measures the resistance between probes to determinethe presence of moisture. To do so, the sensing circuit preferablymeasures how much current can flow between the probes. The challenge ina battery-powered sensor is to measure the conductivity between probesusing a minimum amount of current. Further, the microcontroller uses anadditional amount of energy as it must wake up periodically to measurethis current flow.

The design of the present invention preferably employs a classicresistor-capacitor discharge circuit (hereafter also referred to as RCcircuit) (see FIG. 24). There are for example three sense-probe circuitseach comprising a pin (a) of the microcontroller connected to capacitor(C) (whose value is explained below), tied to ground (g) and alsoconnected to a sense probe (Ps) (see FIG. 24). An additional pin of themicrocontroller (b) is connected to grounding probe (Pg), with a fixedresistor (Rg) connecting grounding probe (Pg) to the circuit ground (g).When moisture is present, it presents a resistance (Rm) between probesPs and Pg. As explained below, this forms a classic parallel RC circuit.In operation, microprocessor pin (a) is used to charge the RC circuit,then switch to a hi-z mode and read the capacitor voltage, thus enablingthe calculation of Rm+Rg. Rg is necessary because, once pin (a) hascharged the circuit (and thus becomes an open circuit), the presence ofRm and Rg form a simple voltage divider, enabling pin (b) to detectcurrent flow through Rm.

This voltage divider would be pointless in a circuit with only onesensing probe Ps and one ground probe Rg. However, when a plurality ofsensing probe and grounding probe circuits are employed, the addition ofRg makes it possible for the microcontroller, while charging one of thesensing probe capacitors with moisture present, to detect into which ofthe grounding probes any current is flowing, thus being able to detectprecisely which two or more circuits are in contact with water.

There are preferably three such sense probe and grounding probe circuitsas shown in FIG. 25. With this arrangement, there are thus 9 possibleclassic RC circuits made up of any sense-probe capacitor, any of thethree ground-probe resistors, completed by the presence of moisturebetween any sense probe (Ps1, Ps2, and/or Ps3) and any ground probe(Pg1, Pg2, and/or Pg3). To be clear, any capacitor (C1, C2 or C3) caneach discharge through its associated pin (Ps1, Ps2, or Ps3), throughmoisture (Rm11, Rm12 (shown), Rm13 (shown), Rm21, Rm22 (shown), Rm23,Rm31, Rm32, Rm33), to any ground pin (Pg1, Pg2, Pg3), and finallythrough the pin's associated resistor (Rg1, Rg2, or Rg3). Moisture whenpresent typically causes a resistance (Rm) of tens of thousands of ohmsto 2.5 million ohms when the sensor is “wet” to ten to fifty millionohms and more when “damp,” while the resistance is well above 1000million ohms, when the probes are “dry”.

The microcontroller preferably provides two methods of reading thevoltage level of pin (a)—either by taking a fast, lower-powered digital(0 or 1) reading, or slower analog (as in analog to digital conversion)reading that requires more power. By selecting the appropriate value forRg (Rg1, Rg2, Rg3), the present embodiment of the invention can workwell with either. Because a digital reading results in a “one” when pin(b) is above approximately 50% of the supply voltage and a “zero” whenbelow approximately 50% of the supply voltage, the present inventionarranges the moisture resistance (Rm) to form the upper half of voltagedivider a-Rm-Rg-g, with the ground-probe resistor (Rg) comprising thelower half of the voltage divider, with the microcontroller pin (b) inthe middle. Thus, because when moisture is present, the resistance ofthe moisture between probes on the sensor can range as high as ten MΩfor a “damp” condition, one embodiment of the invention preferablyemploys a ground-probe resistance of approximately ten MΩ (though theinventors anticipate other values of Rg may be more optimum given thetradeoffs of accuracy, current usage, sensitivity, etc.). Thus, onemoisture sensing circuit comprises a capacitor (C) tied to ground (g)and its sense probe (Ps), a resistor (Rg) tied to ground (g) and itsground probe (Pg), the moisture resistance (Rm) between sense probe (Ps)and ground probe (Pg), and two microcontroller pins (a) and (b), one oneach side of the moisture resistance (Rm).

In one embodiment of the current invention, under normal operation whereno moisture is present, the microcontroller periodically wakes up,verifies the capacitors C1, C2 and C3 have not lost their charge due tothe presence of moisture, then provides a “topping off” charge andreturns to sleep. In one embodiment of the present invention themicrocontroller awakens every two seconds. As to the value of thecapacitors, because the current (but by no means only) embodiment of theinvention awakens every two seconds, the value of the capacitors must bechosen so that the presence of moisture to any important degree mustdischarge the capacitor to a voltage of less than half its fully chargedvoltage within two seconds. By the classic RC discharge equationV=Vo*e{circumflex over ( )}(−t/RC), solving for C yields the equationC=−t/(R*ln(V/Vo)). Considering R=Rg+Rm, and that Rg must be on the orderof ten million ohms because “damp” bordering on “wet” moisture impingingon the probes Ps and Pg produces a resistance on the order of tenmillion ohms, R=20 MΩ. Further, considering the design goal of theremaining charge on the capacitor in the presence of minimal (or “damp”)moisture must discharge to 50% of its initial charge, V/Vo=0.5. Further,given the sleep time of the microcontroller in the current (but by nomeans only) embodiment of the invention is 2 seconds, C must be lessthan or equal to 0.144 uF. With the proper values of the sense andground circuit established, the microcontroller can periodically, or bymeans of a microcontroller interrupt, quickly and easily determine thepresence or absence of moisture. Using the microcontroller's wake fromsleep interrupt feature, sleep times of longer than 2 seconds arepossible (with appropriate adjustments to the value of C1, C2 and C3)without any risk of sleeping through a leak event, thus conserving thebattery. The inventor has determined however that a more appropriatevalue for C is far less, as will be seen below.

Considering the same sequence above, but now with moisture present, themicrocontroller periodically wakes up, and in sequence and one at thetime checks the remaining charge on each capacitor C1, C2 and C3. Ifmoisture is present to any degree, as established above, the capacitor'svoltage will have fallen below 50% of its original charge, and thus theassociated microcontroller pin will read as “zero”. Upon reading a“zero” for any of the sense probe capacitors, the microcontrollerinstantly changes pin (a) to an output, recharging the capacitor. Whilethe capacitor is being charged, the voltage of pins Pg1, Pg2 and Pg3 areread either as a digital value (as in the current but by no means onlyembodiment of the invention), or more accurately an analog value (as inanalog to digital conversion) along with the attendant increase batterydrain. The importance of the improved accuracy can be weighed againstthe increased battery load to determine the best course of action.Having charged the capacitor and read Pg1, Pg2 and Pg3, themicrocontroller changes pin (a) back to an input, waits a fixed,predetermined period of time, then performs an analog reading (as inanalog to digital conversion) of the voltage remaining on the capacitor.The voltage remaining is a function of the moisture resistance Rmbetween Ps1 and Pg1, Pg2 and/or Pg3. The actual moisture resistance iscalculated, again, using the classical RC discharge equationV=Vo*e{circumflex over ( )}(−t/RC), where R=Rm+Rg. Substituting for R,and solving for Rm yields the equation Rm=−t/(C*ln(VNo))−Rg. Thus, themoisture resistance Rm can be calculated to a reasonable accuracy. Loweris wetter, so a much smaller capacitor allows for reading extremely highresistances.

Three important facts are here noted: first, the moisture resistancebetween Ps1 and Pg1 is in reality almost invariably a different valuethan Ps1 and Pg2, and again a different value between Ps1 and Pg3. Forthe sake of clarity, it is herein referred to as simply Rm, but thereare in fact 9 possible resistance values between all the combination ofsense (Ps1, Ps2, Ps3) and ground pins (Pg1, Pg2, Pg3); second, theremaining voltage on the capacitor in the presence of moisture is moreaccurately a function of the resistance between the sense pin and 3ground pins and the number of ground resistors included in the classicRC circuit as a result of the moisture impinging on the various senseand ground pins. In fact, if all the sense pins and ground pins arefully wet, the individual sense and ground circuits become part of alarger mesh circuit thus introducing an error into the equation above.Taking an analog reading of each of the ground pins as noted above willresult in the ability to take much more accurate measurements of thevarious moisture resistances impinging on the various sense and groundprobes; third, other embodiments of this invention can include differentnumbers of sense and ground circuits without affecting the uniquesensing features of this invention.

It is also worth noting here that in the current (but by no means only)embodiment of the present invention, the actual value of the sensecircuit capacitor C can be chosen to allow for the maximum resistancereading resolution based on the fact the capacitor voltage initiallydrops precipitously, then slows (exponentially of course) as the voltageapproaches zero. The inventors determined experimentally that anappropriate capacitance includes 2700 pF, though other values may bemore desirable when considering cost. The optimal value should also bedeterminable with a closed form equation if so desired. The inventorshave also anticipated that other values for sense capacitor C and groundresistor Rg would work equally well, and with further research, othermore optimal values would be found to exist by experimentation and/ormathematical calculation.

Further, the current embodiment of the sensing circuit when activelysensing moisture, having a capacitance of 2700 pF and being chargedapproximately every 2 seconds to approximately 3 volts, by the capacitorcharge equation, Q=CV, the sensing circuit dissipates 2700 pF*3V=8.1 nC(nano-Coulombs) every 2 seconds. By the current flow equation, I=Q/t, itcan be seen the moisture sensing circuit dissipates a maximum average of4 nA (nano-Amperes). This significant feature both preserves batterylife and greatly limits the phenomenon of electrolysis between sense andground probes, prolonging the life of the sensor.

Anticipated sensing circuit and invention embodiment variations

The current (but by no means only) embodiment of this invention isdesigned to measure the electrical resistance of moisture impinging onone or more probes either in contact with a surface, or separated fromthe surface so as to differentiate between relatively minimal surfacecondensation and more copious amounts of water associated with an actualleak. However, in addition to measuring water, any number of variousembodiments of this invention will allow measuring the variation of bothmuch smaller and much larger resistances by altering: 1) the sensecircuit capacitance C, with much larger capacitance values adapting thecircuit to read much smaller resistance values, and conversely muchsmaller capacitance values adapting the circuit to read much largerresistances exceeding 1000 MΩ values being limited only by the leakagecurrent of the capacitor, microcontroller input impedance, leakagethrough other circuit elements and circuit board substrate—althoughthese leakage currents themselves could be used to take a relativemeasure of ambient moisture and other physical properties.

Further, various other embodiments of the present invention could employpiercing probes, electrical connectors, magnetically coupling contacts,conductive plastics, and any other electrically conductive means ofemploying the sensing and ground circuits for the purpose of measuringthe fixed or varying electrical resistance of any substance, atmosphere,substrate, etc.

Further, there is no limitation to the number of types of substances,atmospheres, substrates, etc. that the present invention in its plenaryembodiments could measure.

By example, but not by means of limitation, a novel embodiment of thisinvention with piercing probes for Ps and Pg, with appropriateadjustments to the sense probe capacitor C and ground probe resistanceRg, and appropriate changes to the sensor programming, the varyingelectrical resistance of gypsum wall board may be measured, therebyemploying the gypsum wall board as a substrate for measuring the ambienthumidity of the airspace on both sides of the wallboard, enabling thedetection of occult moisture accumulation in otherwise inaccessibleairspaces in attics, floor systems, walls, etc. The inventors anticipatethe ability of this embodiment to detect such occult moisture several,if not dozens, of feet away from the moisture source. The state of thesubstrate itself preferably will also be monitored for excessivemoisture. Further, the piercing probes themselves can also serve as theaffixing means of the sensor to the gypsum wall board, and owing to thesensor's light weight, requiring no other affixing means. As such,extreme ease of installation is also an important feature of thisembodiment.

Also by example, but not by means of limitation, those skilled in theart would recognize the current invention could be simply embodied withthe appropriate attaching and electrical coupling means to make easyinstallation and useful measurement of the electrical resistance of anynumber of construction and retrofit materials including (by means ofexample and not limitation) concrete, Masonite, HardiePlank, etc.Further, appropriate embodiments of the current invention could beinstalled in certain substrates such as (by means of example and notlimitation) concrete, closed-cell and open-cell foam insulation, etc.Further, appropriate embodiments of the current invention could bedeployed usefully in certain applications not requiring affixing means,such as (by means of example and not limitation) “tossed” onto the topof or inside of batt and blown-in fiberglass insulation, paperinsulation, etc.

Also by example and not by means of limitation, those skilled in the artwould recognize the current invention could be embodied with detachableprobes themselves appropriate for permanent installation into virtuallyany construction material with both simple and elaborate electricalconnection means. These probes could be installed during construction,retrofit, or at the time of manufacture. By means of example and notlimitation, extended lengths of electrically conductive strips spacedappropriately, affixed either during manufacture, retrofit orconstruction, and connected properly to an appropriate embodiment of thecurrent invention, could monitor extended areas of walls, floors, roofs,etc. for significant changes in moisture. Further, by means of examplenot by means of limitation, detachable probes in the form of paddles,fins, shims, pins, screws, nails, bolts, tapes, plastics, etc. could beemployed, either of special manufacture for the specific purpose ofserving as detachable probes, or of common manufacture.

Further, manufacturers of common construction products could offerversions of their products with such probes already included. Suchversions would add minimal cost owing to the simple methods required toinstall such probes. By example and not by means of limitation,conductive adhesive tapes could be applied from continuous rolls onto,for example, batt insulation backing.

Further, additives designed to enhance the variation of resistance,capacitance, or inductance due to variations in moisture, mechanicalstrain, microbial activity (including damage to the substrate oradditive possibly resulting in lower resistance, or additives whosemetabolic products result in the substrate exhibiting higher or lowerresistance), corrosion (such as sacrificial probes), electrochemicalreactions, etc. could be employed. Electrochemical activity would beread as negative resistance.

Also by example, but not by means of limitation, the current inventioncould be embodied with hydrophobic treatments to control how moisture,both condensing and accumulated, interacts with the enclosure of theinvention, and with its various moisture probes. The hydrophobic surfacewould control the formation of condensation on key areas of theinvention, improving the accuracy of the invention to discriminatebetween leaks and condensation. Further, hydrophobic treatments woulddiscourage the adhesion of accumulated moisture on the proximal areasbetween the invention and the monitored surface, as during a leak event,thereby tending to accelerate the evaporation of moisture beneath theinvention, further mitigating the need to remove the invention to clearaway moisture from beneath. This accelerated drying would reduce thetendency to grow mold. By means of example and not by means oflimitation, hydrophobic treatments could be added between the probesthemselves, but not between the probes and the edge of the invention,thereby allowing a channel for the moisture to form a connection betweenthe probes, but to otherwise prevent condensation on the inventionitself to form a conductive path between probes.

This hydrophobic treatment can be applied by making the bottom of thesensor out of suitable hydrophobic materials, or by coating the bottomof the sensor with a hydrophobic composition or compositions. Examplesof suitable hydrophobic materials will be apparent to those of ordinaryskill in the field of hydrophobic material manufacture. Examples ofsuitable hydrophobic compositions include Rain-X® Original Glass WaterRepellent and ink additives such as those from Cytonix. These additivescould be adapted for use in the circuit board manufacturing process.Preferably, the hydrophobicity of the compositions or materials issufficient to cause water to bead at standard temperature and pressure,at sea level, on Earth, or under any other intended environment andcondition.

Processing the Data

The internal processor and transmitter preferably relay the currentstate of the resistance of moisture impinging on the various sense andground probes. Reporting the relative resistance between the probes,rather than a binary moisture/no-moisture condition, enables the sensorto relay the fact that a moisture condition exists, and if the moisturecondition is advancing or receding. This is a significant feature,allowing the sensor in certain situations to deduce that the leak slowand growing, or has stopped and is drying even though the probes arestill in contact with a moist surface. This then allows the sensor to bepermanently attached to a surface, or to be deployed in locations thatare difficult to access, without the need to dry the surface after aleak event.

The current (but by no means only) embodiment of the design has twoestablished thresholds of measured resistance between any of the senseand ground pins that trigger special conditions. The “damp” threshold ispreferably set to approximately 50 MΩ. The second threshold ispreferably set to approximately 2.5 MΩ, the measured resistance of tapwater standing on a clean surface. Hysteresis is also employed. Ofcourse, resistances above the “damp” threshold are considered “dry”.

Preferably, under normal, dry conditions, the sensor waits for amoisture condition to occur, and reports the resistance reading of eachsense probe very infrequently, such as every 6 hours.

In operation, if the resistance measured by any of the sense probesdrops below the “damp” threshold, the invention begins periodicallytransmitting the actual resistance each sense probe measures, along withany ground probes that are also wet. These transmissions are much morefrequent, such as for example once every 15 minutes. This is a verysignificant feature. If the resistance continues to drop until below the“wet” threshold, triggering an alarm, the resistance readings leading upto the alarm will be available, producing a much more meaningfuldataset. Essentially, a “fingerprint” of the alarm event is produced,identifiable by human analysis or more importantly by computeralgorithms.

In operation, if the invention measures a sudden drop in resistance froma “dry” condition to a “wet” condition, it preferably transmits themeasured resistance, which sense probe is detecting the “wet” condition,and which ground probes (Pg1, Pg2 and/or Pg3) are also wet. It repeatsthis transmission for example once a minute for 5 minutes. The sensorcould also store and report the previously measured resistances prior tothe “wet” condition, providing more data about conditions prior to the“wet” event, enabling the production of much higher quality graphs forhuman analysis, and datasets for algorithms.

The current (but by no means only) embodiment of the invention, in everyfacet, endeavors to generate meaningful data to aid in the manual andautomatic discrimination of genuine leak events from false alarms, suchas accidental spills, the normal accumulation of condensation, etc. Thevalue of these features in a leak detection and prevention system cannotbe overstated. False alarms significantly decrease the value andeffectiveness of any alarm system.

The inventors anticipate the current number of sense and groundcircuits, component values, reporting thresholds and frequency, andevery other facet of the design are not yet optimal, and yet already areyielding significant improvements in accuracy.

The sensor preferably employs an accelerometer that detects and reportsboth movement and the orientation of the sensor. It also preferablyrelays the sensor's orientation via readings from the accelerometer.Other data are also preferably relayed, including the current batterystate, etc.

The sensor preferably employs an internal temperature sensor. Thecurrent sensor temperature is preferably transmitted with all resistancereadings and is correlated with the resistance readings. Temperaturefluctuations correlated with resistance readings greatly improve theability to discriminate between actual leak alarms and false alarms.Further, the sensor preferably sends periodic transmissions so that thereceiving processor can verify the status of the sensor, as well as theradio signal strength. During the periodic update, any changes in thestate of the sensor are also transmitted, but only if changes occurred.By omitting redundant data, the battery power can be conserved.

Anticipated Improvements to the Current Embodiment

The current (but by no means only) embodiment of the invention capturesand reports the resistance and state of the various moisture probes, thetemperature of the sensor, and the orientation of the sensor with anaccelerometer. The inventors, in fact, anticipate the addition of manyother types of physical property sensors to capture the physical stateand activity of the space around a leak detector, both ambient/generalphysical properties and targeted physical properties. The inventorsanticipate the commercial value of correlating and analyzing gathereddata from many such similar spaces, such as for example one sensorbehind the toilet compared to other sensors in other bathrooms behindthe toilet, or one sensor under the refrigerator compared many othersensors under refrigerators. The inventors anticipate comparing andcorrelating the data from one-versus-many comparisons of sensors innumerous locations. The inventors also anticipate useful one-versus-manycomparisons of sensors in dissimilar locations.

By example (but not by means of limitation) the inventors anticipaterecording and transmitting the state of artificial lighting, level ofambient noise, relative humidity, temperature, electrical power usage,water usage, etc. of a space to provide clues to the events leading upto a leak alarm. This data could, for example greatly aid in determiningif a bathroom floor sensor alarm has detected a genuine leak, anaccidental spill from the shower curtain, or condensation.

This data could also, for example, be used to determine the occupancystatus of a residence. This method, of correlating lighting, humidity,temperature, and other ambient values enables a much more efficient andcost-effective method of detecting occupancy, as compared to, forexample, passive infrared (PIR) battery-powered motion detectors. Thisis because the PIR sensing element requires much more power, limitingbattery life.

Further, the inventors anticipate correlating this data both in the timeand frequency domain by use of for example (but not by limitation)Laplace transforms, Z transforms, S transforms, and various othermethods.

Further, the inventors anticipate that a constellation of variousembodiments of the current invention will enable the inexpensive captureand analysis of many other physical properties pertaining to, andcorrelating with, both actual leak alarms and false alarms, in both thetime and frequency domain. For example, the inventors anticipate thecorrelation of measured moisture probe resistance, sensor temperature,nearby gypsum wall board conductivity (as a novel means of detectingrelative humidity), ambient light, ambient sound, etc. could aid indiscriminating between false and genuine leak alarms.

In addition to the discrimination between false and genuine leak alarms,or leak prevention in general, the captured data of the various physicalproperties both named and anticipated above, together with thecorrelated data from a constellation of such sensors, can also aid inmore accurately determining many other states pertinent to a physicalstructure, such as for example occupancy (of one room among other rooms,a dwelling in general, etc.); the general habits of occupancy;operational state, efficiency, etc. of the air conditioning, heating,etc.; general building health concerning relative humidity, thelikelihood and prediction of mold formation; even the prediction andeffectiveness of improvements to air conditioning, additional wall andattic insulation, etc.

The inventors anticipate that, although a reporting a range of sensorvalues is very advantageous, whether as a range of resistance,capacitance, temperature, humidity, etc. These readings, in fact, can bethought of as a multiplicity of sensor states. Thus, the readings can bereported as finely as is useful, or as coarsely as is practical. Theresistance readings (for example) can be reported with any resolution,with the attendant increase in bandwidth, battery power, micro-processorcycles, etc., or with as little as 1 bit, all while being an improvementover the 1-bit (i.e. 1=wet, 0=dry) reported by currently availablemoisture sensors. The inventors further anticipate, with a givenresolution (such as, for example, 2-bits thus 4 values, or 10-bits thus1024 values), each available value within the given resolution maycorrespond to a measured physical state or value, whether linearlyand/or logarithmic and/or non-linearly with each value representing arange or group of physically measured values, carefully selected suchthat the transmitted value is more meaningful and efficient.

For example, the measured resistance between probes for the purpose ofmeasuring moisture can be, of course, representing with 2 binary states(1-bit) as 1=wet (for resistances below, say, 2.5 million ohms) and0=dry (for resistances above, say, 2.5 million ohms plus 0.5 millionohms for hysteresis). The resistance could also be represented in 4states using 2 bits, with “00” representing a “saturated” condition whenthe measured resistance is below 1 million ohms, “01” representing a“wet” condition for resistances between 1 million and 2.5 million ohms,“10” representing a “damp” condition for resistances between 2.5 millionohms and 50 million ohms, and “11” representing a “dry” condition.Alternatively, the range from 1 million ohms to 100 million ohms couldbe divided evenly or logarithmically by 4. If the resistance is conveyedin 3 bits, for example, the lower 4 values could represent 100,000 ohmsto 10 million ohms divided evenly, while the upper 4 values couldrepresent 10 million ohms to 200 million ohms divided logarithmically.

It should be noted the inventors anticipated transmitting any value(whether physical and/or derived and/or conceptual) using any number ofbits of data, with each value representing one or a range or ranges(continuous and/or separate) of meaning.

It should be noted the inventors anticipated the utility of signalingthe state of a sensor by quantization other than binary bits. Otherdiscernable entities of quantization also apply, whether bits and bitstates, fractions of voltage, fractions of amperes, types and methods ofmodulation, transmission frequency, modulation frequency, etc. and alltheir combinations, etc. with the selective employment of each in agiven transmission carrying meaning. Such as, for example, a 4-bitbinary message transmitted with AM modulation carrying a differentmeaning than an identical 4-bit binary message transmitted with FMmodulation.

By employing serrated edges around the circuit board as shown inFigures, the surface area of the trapped water can be greatly increased,thereby increasing the evaporation rate of the entrapped moisture. In analternate embodiment, a moisture removal aid 30 as shown in FIG. 15 canbe affixed to the bottom of the circuit board employing channels thatterminate beyond the perimeter of the circuit board as shown in FIGS.16-17, with three advantages: first, the volume of water is nowdisplaced by moisture removal aid 30; second the channels added tomoisture removal aid 30 tend to wick water into them, and out to theserrated edges; and third, The serrated edges of moisture removal aid 30further increase the surface area of the water volume, thus greatlyincreasing the evaporation rate. Aid 30 could be rectangular with somewindows cut out to allow water to reach the sensors without beinghampered by moisture removal aid 30.

Further, by employing a pattern of hydrophobic and hydrophilic areas,water can be further induced to follow these channels out to theserrated edges for vastly improved drying rates. For example, the bottomof the sensor can be hydrophobic or hydrophilic, and treated with amaterial which causes the treated area to become hydrophilic orhydrophobic, respectively (or if the bottom of the sensor is neithersufficiently hydrophilic or hydrophobic to begin with, then it can betreated with treated with materials which cause part of the treated areato become hydrophilic and part to become hydrophobic. The treated areacould be in the pattern shown in Figure, or in some other pattern whichpromotes movement of water and evaporation.

Further, there are a range of substances that change in color,fluoresce, etc. when in contact with moisture. The addition of anappropriate substance to the exterior of the sensor, whether in the formof paints, dyes, dyestuffs, additives, etc., would cause the color ofthe exterior of the sensor to change when in contact with moisture,making it much easier to ascertain by visual inspection that water ispresent, solving a common problem encountered by the inventors where asensor, having accurately detected moisture, is inspected by someoneunfamiliar with the function of the moisture sensor. Because the amountof water is typically small (owing to the fact the sensor detected aleak and shut off the water), someone unfamiliar and thus unaware that avery close inspection is necessary, then assumes in error no water ispresent implying a false alarm—a situation not conducive to good willtoward the sensor.

But with the addition of an appropriate substance to the exterior of thesensor, a vivid change in physical appearance of the sensor would reducethe likelihood of someone unfamiliar with the sensor falsely assuming nomoisture is present. Further, where appropriate, such a substance couldbe employed as a consumable application to the exterior of the sensorsuch that, upon contact with moisture, dissolves into disperses throughthe impinging water, more effectively flagging the presence of moistureon the sensor. Further, a substance may be deployed, not only to theexterior of the sensor body, but also to an appliance appurtenant to thesensor, or applied the adjacent surface. Further, the color-changingdissolving dye may be reversible where the dye reverts to its formerstate when the water dissipates. Further, the dye may be sufficientlyvolatile so as to evaporate, negating the need for clean-up. Further,the dye can be effervescing (i.e. foaming) to further exaggerate thepresence of moisture. Further, it may be desirable for the additive toproduce a discernable odor when in contact with moisture.

An advantage of the present invention is its ability to remotely andautomatically search for leaks, not just using easy methods (like abasic leak sensor behind the toilet), but by employing methods thatallow one to differentiate between a genuine leak (e.g., a toilet fillerline break) and a false alarm (e.g., someone in the shower with theshower curtain out). Further, its utility is enhanced by its ability todetect leaks amid sensor noise, such as by watching the flow meter forsigns of water usage anomalies (when for example the sensor of thepresent invention is used with the leak detection system disclosed inInternational Publication Number WO 2017/019801 A1, published 2 Feb.2017, assigned to ENCO ELECTRONIC SYSTEMS, LLC, and incorporated hereinby reference).

The following features of the leak sensor of a preferred embodiment ofthe present invention, improve the ability of the present system todetect genuine leaks and false alarms.

Adding an ambient light detector to the sensor allows one to:

determine if someone turned on a light in the room just prior to a leakdetection event; infer general occupancy by locating the sensor on theceiling near a light.

Adding a humidity sensor to the device allows one to correlate changesin humidity with the leak detection event, such as shower curtains leaksduring a shower.

Adding piercing probes to the sensor facilitates installation of thesensor directly into the gypsum wallboard on ceilings, walls, etc. Asgypsum's conductivity changes measurably with even minute changes inrelative humidity, one can periodically measure its conductivity, thus:

allowing the detecting of nearby leaks behind the wallboard, such asbelow the toilet on an adjacent floor;

allowing one to detect the presence of leaks farther removed as therelative humidity in the airspace behind the wallboard will increasesignificantly, enabling the detection of occult leaks such as: firesprinkler system leaks; roof leaks; exterior wall leaks; and leaks inriser chases that terminate above the ceiling;

allowing relative reading of ambient humidity in the air, so that onecan detect: the probability that the shower is being used; chronic highrelative humidity conditions that allow mold growth; and potential HVACproblems.

FIGS. 12-14 are schematics of a ceiling sensor of an embodiment of thepresent invention. As can be seen, this is also a resistive sensor, butwhose major difference is that it has multiple capacitors it can use toread a much larger range of resistances, such as those found insheetrock, ranging from 1000s of megohms to less than 1 ohm.

By adding an ambient noise level sensor, one can:

infer occupancy using a much less costly method than motion detectors,as motion detector elements require a large amount of current, requiringlarger batteries that require more frequent changes;

correlate leak events with ambient noise, such as detecting that theshower is running; possibly detect problems with certain appliances suchas refrigerator compressor problems, or even that the compressor isrunning too long because the door is left open; correlate flow meteractivity with appliances that frequently use water especially whenliving space is unoccupied, such as ice makers, dishwashers and washingmachines.

About ten moisture sensors could be used in a typical condo unit, thoughoften there could be 12-15 per unit or even more.

In addition to measuring the presence of water by a change inresistance, by the addition of a capacitive sensor made up of twoinsulated, parallel traces on a PCB (printed circuit board) or any othersuitable substrate, the sensor can measure the total volume of watercontained beneath or in the proximity of the sensor. These paralleltraces compose a low-valued capacitor with the PCB, and surroundingenvironment serving as the capacitor's dielectric, by virtue of the factthe parallel traces form a capacitor with a very high fringe-to-plateratio. In other words, much of the capacitance is contributed by thefringe electric field radiating around the comparatively thin parallelsurface area made up of the adjacent trace edges. See Palmerhttps://arxiv.org/ftp/arxiv/papers/0711/0711.3335.pdf. Air has adielectric constant of approximately 1, typical fiberglass circuitboards have a dielectric constant of approximately 4. Water has adielectric constant of 75 to 80—far more than any other materialtypically found in the home. By virtue of the fact this capacitor isphysically distributed, and can be considered a series of parallelcapacitors, the capacitance can change dramatically, and crucially, inproportion to the volume of water near the parallel trace capacitor.

By employing multiple conductive traces in parallel, both co-planar andon adjacent layers, and by selectively powering, grounding, and readingthe different traces, the electric field generated by the traces duringa measurement can be shaped. Thus, the sensing direction can be alteredwithout the substrate having to be physically re-oriented. If theplurality of traces were positioned along the edge of a substrate, theamounts of water impinging on the upper surface, lower surface, andalong the edge of the substrate could be measured independently using aminimum of microcontroller resources.

By employing direct, alternating, and high frequency signals selectivelyto the several conductive traces (both in phase and out of phase), whilereading the resulting voltage and current of other traces, the type ofmaterial impinging on the generated electric field may be inferred fromits dielectric constant at different frequencies.

By combining the relatively high sensitivity of a resistance measurementwith the lower sensitivity of the parallel trace sense capacitor—that isalso sensitive to the volume of water impinging on the parallel traces,the present invention can provide a superior moisture sensor capable ofdiscerning the difference between a damp surface, or even a conductivesurface, and surfaces with water. This is a great technical advantagefor sensors located in areas that may frequently get damp or even comeinto contact with a limited amount of water, such as by the shower wherehumidity and accidental spills are possible. Though these spills aredetected as leaks, they are ultimately false alarms. Thus, thiscapacitive sensing method is able to greatly increase the value of aleak detection system by reducing the number of false alarms.

The actual capacitance can be measured, among other means, byconstructing a typical parallel RC circuit, and by charging this circuitand then measuring the discharge time. Thus, a volume-sensitive moisturesensor can be very inexpensively constructed. In addition to paralleltraces on a substrate, the capacitive sensing element can be constructedfrom multi-conductor wiring that can be installed around the perimeterof a room, in the walls during construction (both interior andexterior), and the presence of water easily detected.

A further advantage of this moisture measuring method is that theconductors comprising the sensing capacitor can be completely insulated,thus protecting the sensing element from corrosive chemicals and salts,including those found in the home, such as floor cleaning products, saltair in coastal communities, etc.

A further advantage is that the measurement waveform's frequency contentcan be independent of those otherwise already present on the wire,enabling the measuring waveform to be differentiated from a waveformalready present in the wire. Thus, a circuit may be employed thatmeasures the capacitance of energized wiring to detect the presence ofmoisture along the wiring. Thus, existing wiring in the home may beemployed as moisture sensors, both low-voltage and high-voltage wiring,whether used for other purposes or unused. The inventors anticipate, forexample, measuring sinusoidal high-voltage wiring at the same waveformposition (such as, for example at peak voltage, at zero-crossing, orsome other optimal point taking into consideration random linear andnon-linear loads). Preferably the measurement is taken nearzero-crossing at a voltage below the rectifier forward voltage.Capacitance from moisture impinging on the wiring can be furtherdetermined by frequency analysis. The inventers anticipatediscriminating the dielectric permittivity (both real and imaginary) ofwater from other sources of capacitance by measuring permittivity vsfrequency (as covered here:https://www.nature.com/articles/srep13535#fl).

While capacitive liquid level measuring has been known for some time, itis not known by the inventors to be currently in use with anycommercially available residential or commercial moisture sensors.

In FIGS. 29-31 one can see that the electric field generated by thecapacitive structure can be steered by changing the polarity of aplurality of conductors. The capacitance of the parallel conductors isstrongly affected by the dielectric constant of the medium in which thee-field extends.

By steering the e-field, the presence of water can be detected indifferent areas around the sensor. One, but by no means only, embodimentof a moisture sensor employing capacitive sensing is as follows. Acontinuous conductor (referred to as Steering Trace 1) is deployed ontoa structure (such as, for example, around its perimeter), and attachedto the pin of a micro-controller. Additional conductors (referred to asZones 1-5) are deployed in parallel and in close proximity to SteeringTrace 1, each connected individually to a micro-controller pin. Twoadditional conductors (referred to as Steering Trace 2 and Top SteeringTrace 3) are also connected individually to micro-controller pins. Zones1-4 are placed between Steering Trace 1 and Steering Trace 2 and are allco-planar. Steering Trace 3 is on the opposite side of the circuit boardand parallel to Steering Traces 1, 2 and Zones 1-4. Further, Zones 1-4are connected to electrical ground through a fixed resistor (such as 10million ohms).

The geometry of Zones 1-4 are such that moisture impinging on theperimeter of the sensor can be detected. Zone 5, located across theinterior of the bottom of the sensor, can be used to detect that waterhas completely covered the area beneath the sensor, and thus is afurther measure of the amount of moisture in contact with the sensor.The inventors have anticipated many other capacitor geometries for thepurpose of detecting moisture, including interlacing fingers, spiraldesigns, multi-layer rows and columns, etc., along with the likelybenefits of each, especially increased sensitivity to moisture in theadjacent surface, using numerous zone elements to render a 2D or 3Dimage, mathematically extracting virtual zones from numerous zoneelements, using tighter circuit tolerances and to measure relativehumidity, etc. FIG. 31 depicts the referred to steering traces and zonesof an embodiment of a moisture sensor employing capacitive sensing.

Continuing, the micro-controller is programmed such that, to measure thecapacitance of any of Zones 1-5, the following steps are executed usingZone 1 as the example: 1) connect Steering Trace 1 to electrical groundvia programming in the micro-controller; 2) connect Zone 1 to theelectrical supply via programming in the micro-controller; 3) change themicro-controller pin connected to Zone 1 to a high-impedance input.Because of the capacitance between Steering Trace 1 and Zone 1, and thefixed resistor connecting Zone 1 to ground, a simple RC circuit isfashioned. In turn, each of Zones 1-5 can thus be measured.

Continuing, if (again, for example) Zone 1 is measured with SteeringTrace 1 grounded, then of course the electric field formed between Zone1 and Steering Trace 1 would “sense” moisture along the region betweenZone 1 and Steering Trace 1. If, however, Steering Trace 1 were left ina hi-z state, Steering Trace 2 were grounded, then the moisture betweenZone 1 and Steering Trace 2 would be measured.

Further, if Steering Trace 1 were connected to the electrical supply,with Steering Trace 2 grounded, and Zone 1 measured, the electric fieldformed between Zone 1 and Steering Trace 2 would be slightly repelled bythe energized Steering Trace 1. Further, If Top Steering Trace 3 wereenergized, the electric field formed between Zone 1 and Steering Trace 2would be further affected.

Further, if Steering Trace 1 and Zones 1-5 were energized, SteeringTrace 2 grounded, and Top Steering Trace measured, the electric fieldwould be directed outward in the plane between the top and bottomtraces. In other words, the moisture impinging, not beneath, but ratherbeside the sensor could be independently measured.

In short, selectively energizing and grounding the various traces inthis example can be used to “direct” the sensing electric field, thussteering the moisture sensing region. And though the conductive geometrydescribed in this example is producing a great improvement over existingmoisture sensors, the inventors anticipate optimizing the sensor furtherwith refinements to the precise geometry of the conductors, the spacingbetween the conductors, making use of materials other than circuitboards, employing additional circuit board layers, etc.

Two basic methods of reading the capacitance of the parallel tracecapacitor (and thus the relative amount of water impinging on thesensor), that also require very little power, employs the circuit inFIG. 24, a basic RC circuit formed by a resistor and the parallel tracecapacitor. Method 1 uses a charge/timed discharge procedure, method 2uses a timed charge/voltage measurement procedure. The value of themethods below, in addition to other methods anticipated by theinventors, is that these can be implemented in a very efficient mannerespecially useful in battery-powered circuits by virtue of the factthese methods require very little time (on the order of micro-seconds)to complete, and require very little power.

Method 1

The RC circuit is fully charged, then the time for the circuit todischarge down to Vt is measured. If Vc/Vt is constant (ie, Vt is apercentage of Vc such as in a voltage divider), the discharge time isnot affected by Vc (such as in a battery powered circuit). This is seenby solving the RC discharge equation Vt=Vce{circumflex over ( )}(−t/RC)for t, thus t=(−RC)/(ln(Vc/Vt)). Because Vc/Vt and R is are constant, tvaries linearly with C.

The capacitance of a parallel strip capacitor that is short in length(on the order of inches) is, of course, small on the order ofpicofarads, requiring a rather large R. A current embodiment of thecircuit uses a 10 MΩ precision resistor to limit measurement variationsin production. The inventors have implemented and anticipate severalimprovements to method 1, such as: adding a plurality of capacitancesensing circuits to measure various regions of the sensor; using amicro-controller to charge and measure the various sensor capacitances;measuring and applying offsetting values to the measurements (bothduring production, during installation and in situ) to negate parasiticcircuit and ambient environment capacitances; varying the comparator Vtthreshold to facilitate measuring much larger ranges of capacitance;varying R to facilitate measuring much larger ranges of capacitance;eliminating the comparator circuit and instead utilizing the digitalbuffer input typical on a micro-controller (i.e. TTL buffer, Schmidttrigger, etc.); utilizing high dielectric constant substances (such astitanium dioxide, glycerin, etc.) to calibrate the circuit moreaccurately during manufacturing and to incorporate such substances intovarious sensor mounting fixtures to ensure continued calibration and asa means to detect a tamper condition if the sensor is removed from itsmounting fixture.

Method 2

Charge the RC circuit for a fixed amount of time, then measure thevoltage. Solving the RC charging equation Vm=Vc*(1−(−t/RC)) for C,C=−(t/R)*ln(Vc/Vt). By fixing t and R, it can be seen that Vm varieslogarithmically with C. Both method 1 and method 2 can be embodied in amicro-controller. While method 1 takes advantage of the digital buffer,it is limiting that the digital buffer threshold is fixed. With method2, varying the charging time allows for measuring a much larger range ofcapacitances. The inventors have implemented and anticipate severalimprovements to method 2, such as: in battery powered circuits, Vc isnot fixed (and decreases as the battery discharges), however this can becompensated by measuring Vc; by making t very small, minute variationsin moisture near the parallel trace capacitor can be detected, includingmoisture absorbed into the surface adjacent to the sensor; as well asapplicable improvements noted in method 1.

The inventors have anticipated and employed other methods such as:employing a series RC circuit, measuring the capacitance by measuringthe voltage variation across the resistor; all the variations of methods1 and 2 including measuring the time for the circuit to charge to Vt (asopposed to time to discharge); charging, then measuring the voltageafter a fixed discharge time; employing a buffer amplifier (and varyingthe amplifier gain above and below unity) to further increase thesensitivity and range of the sensing circuit; employing varying andfixed voltage and current waveforms and the attendant harmonic contentanalysis to distinguish various substances based on linear andnon-linear qualities of permeability, permittivity, conductivity,hysteresis, losses, etc. of those substances with respect to frequency,bias, positive and negative orientation (especially as related todiamagnetic and polarized materials); etc.

As mentioned elsewhere herein, a preferred embodiment of the moisturesensor of the present invention incorporates both capacitive andresistive moisture sensing technologies. Doing so allows resistivemeasurements of the adjacent surface to detect minute traces of waterabsorbed into the surface (such as concrete, wood, tile, etc.) becausethe conductivity of the surface is correlated to its moisture content. Alimitation of this embodiment is that the sensor must make positivecontact with the surface, making it problematic to permanently affix thesensor to the surface because, either the permanent affixing apparatusmay prevent the resistive measuring probes from making contact with thesurface, or the probes may prevent the permanent affixing apparatus fromadhering firmly to the surface. The inventors anticipated many solutionsto this dilemma, including spring-loaded probes, spring-loaded permanentaffixing apparatus, etc, all of which include an attendant increase incost and complexity of manufacturing and deployment. However, anothersolution is to use the capacitive sensing circuit to detect variationsin moisture in the adjacent surface. The inventors have anticipated thatmeasuring such extremely small variations in capacitance is difficult toperform accurately. However, changes in the relative value over time,and in relation to other proximate sensors measuring similar ordifferent values (such as for example ambient humidity) can becorrelated to produce meaningful events that are precursors to a leakevent. Thus, one could use a sensor of the present invention with onlycapacitive sensing and still achieve goals of leak detection andharvesting of information prior to and after the leak occurs. Further,an accurate measurement of resistance and capacitance may yield theability to discriminate different liquids, especially discriminating tapwater from water with cleaners, i.e. detect false alarms when the flooris being cleaned.

The sensor may include a novel means of signaling moisture, where one ormore light sources (such as LEDs), facing for example downward on thesensor, illuminate the floor at the edge of the bottom of the sensor.Because water would be impinging on the sensor, the light would tend tospread through the water due to internal reflections. Optionally, therecould be multiple LEDs for each zone in the sensor. These zones includeone each for the four sides, or an LED 50 in the center of sensitivityof each zone (FIGS. 33-34). Of course, the LEDs could be on steadily, orflash intermittently to conserve battery power, or flash with a cadenceproportional to the level of moisture, or a code (such as one flash fordamp, two flashes and a pause for wet). This could solve a commonproblem where sensors are generally located in dark areas (insidecabinets, behind refrigerators, etc.) and the typical user cannot easilysee the water.

FIGS. 27-28 show a capacitive sensor of an embodiment of the presentinvention. Because PC boards have “through holes” that allow traces topass from one side of the circuit board to the other, there is anopportunity for a leak. The conventional solution is to enclose thecircuit in a sealed case. However, the capacitive sensor would not worknearly as well in a case, because the capacitive sensing requires suchclose contact with the water. If a case were used, the parallelconductors would have to be embedded in the case using technologies suchas overmolding adding significant cost, and electrical connections wouldhave to be made between the circuit board and case.

A solution is, as noted herein, to use the circuit board as the bottomof the case, with the parallel trace sensors on the bottom. Applying asolid coat of “silk screen” (the usually white paint used to identifycomponents and add other markings to the circuit board), and asking thePCB company to apply two coats, functions well as very good, evensealant that fills in the “through holes”, and adds a notable increasein physical protection to the bottom traces, while adding almost nocost.

When a large number of sensors is deployed in a system over a longperiod (months and years), occasionally a sensor may be moved out ofposition during cleaning, remodeling, and other living activities.Adding a magnetic detector to the sensor circuit and affixing a magnetto the surface where the sensor is placed during installation, thesensor can signal a tamper alarm if the magnet and sensor are separated(i.e. the sensor was moved). This is an important feature when managingdozens, hundreds, thousands and perhaps millions of sensors. Further,the evaporative means detailed above can be made of a magnetic material,combining the benefits of faster evaporation with assured continuity ofsensor positioning. Further, the magnet evaporative aid can also be madeconductive, combining the ability to sense adjacent surface conductivity(and thus moisture content).

Finally, the inventors have anticipated many benefits of the utility ofcombining any of the several features detailed in this document,including, but not limited to: deploying these technologies of detectingand communicating acceleration, vibration, movement, rotation,orientation, temperature, humidity, lighting, moisture, watertemperature, equipment temperature, etc., not just in the living andmechanical spaces of a residence, but also in the mechanical space ofcommercial, industrial, medical, etc. buildings; anywhere along thebuilding envelope detecting leaks, monitoring humidity, detecting sewagebackups, basement water ingress, etc.; anywhere in the common spacesmonitoring building health, environmental conditions, detectingdangerous conditions (such as low humidity, high humidity, condensingatmosphere) conducive to corrosion, rot, mold growth, deterioration,etc.; combining and processing the data communicated from these severaltechnologies for the purpose of predicting, detecting and assuringbuilding, content and especially occupant wellbeing, health and safety.

The following is a list of parts suitable for use in the presentinvention:

PARTS LIST: PART NUMBER DESCRIPTION 10 moisture sensor apparatus 110conductive sensor 11 enclosure 12 bottom panel 120 capacitive bottompanel 13 contact probe/conductive screw/moisture probe 15 waterproofcoating of circuit board 16 lower surface 18 top section 20probe/contact/conductive region 21 upper surface 22 periphery 27 floor30 evaporation aid for promoting better evaporation/moisture removal aid32 hole through printed circuit board 39 with electrically conductiveedge 34 internal battery 37 probe 38 circuit 39 circuit board 41electrically conductive evaporative aid/conductive spacer 42 conductivespacer contact 50 LED a pin of the microcontroller/microprocessor pin bpin of the microcontroller C capacitor C1 capacitor C2 capacitor C3capacitor g ground P1R resistance sensor probe/screw P2C conductivesensor probe/screw P4C conductive sensor probe/screw P3R resistancesensor probe/screw PADC circuit including Ps3 and C3 Pg groundpin/grounding probe Pg2 ground pin Pg3 ground pin Ps sense probe Ps1sense probe Ps2 sense probe Ps3 sense probe Rg resistor/fixed resistorRg1 resistor Rg2 resistor Rg3 resistor Rm moisture resistance Rm12moisture resistance Rm13 moisture resistance Rm22 moisture resistanceSteering Trace 1 continuous conductor Steering Trace 2 conductor TopSteering Trace 3 conductor Zone 1 conductor Zone 2 conductor Zone 3conductor Zone 4 conductor Zone 5 conductor

All measurements disclosed herein are at standard temperature andpressure, at sea level on Earth, unless indicated otherwise. Allmaterials used or intended to be used in a human being arebiocompatible, unless indicated otherwise.

The foregoing embodiments are presented by way of example only; thescope of the present invention is to be limited only by the followingclaims.

The invention claimed is:
 1. A moisture sensor including: a printedcircuit board; a plurality of moisture probes; a plurality of circuitson the printed circuit board monitoring the moisture probes; a batteryfor powering the circuits; and an enclosure containing the battery andthe circuits, the enclosure having a bottom, wherein the printed circuitboard is the bottom of the enclosure; wherein at least two sets ofprobes are on the bottom of the sensor, one set in direct contact with afloor when the sensor is placed on the floor, a second set separatedfrom the floor, and further comprising a set of conductive pins thatenable the printed circuit board to be spaced from the floor; andwherein the enclosure has four edges, and a pair of the probes arepresent along each edge of the sensor, such that when the sensor isinstalled on any edge, a pair of probes will be in direct contact withthe floor.
 2. The sensor of claim 1, wherein by analyzing the data fromthe plurality of circuits monitoring the plurality of moisture probes,it is possible to detect false alarms, such as a damp mop temporarilysetting off a subset of probes.
 3. The sensor of claim 1, wherein themoisture probes are present in the printed circuit board.
 4. The sensorof claim 1, further comprising an accelerometer that reports the currentposition of the sensor (flat, upright, etc.), and if the sensor isdisturbed.
 5. The moisture sensor of claim 1, further comprising anambient light detector.
 6. The moisture sensor of claim 5, furthercomprising a humidity sensor.
 7. The moisture sensor of claim 6, furthercomprising an ambient noise level sensor.
 8. A method of detectingleaks, comprising using the sensor of claim 7 to monitor an area.
 9. Thesensor of claim 7, further comprising a temperature sensor.
 10. Thesensor of claim 9, wherein the temperature sensor is in the moisturesensor enclosure.
 11. The sensor of claim 10, wherein the temperature istransmitted with moisture sensor data.
 12. The moisture sensor of claim1: wherein the moisture probes include electrical conductors in or onthe enclosure; wherein the circuits for monitoring the moisture probesinclude a capacitive sensing circuit on the printed circuit boardelectrically connected to a pair of the electrical conductors formeasuring a volume of water in a space near the enclosure by measuringthe capacitance between the conductors in the pair of the conductors;wherein the moisture probes include sensing contacts on the exterior ofthe enclosure; wherein the circuits for monitoring the moisture probesinclude resistance sensing circuits to allow measurements of electricalresistance between at least two sensing contacts representing a relativelevel of moisture present near the sensing contacts; and furthercomprising: a timer to cause periodic measurements of electricalresistance between at least two sensing contacts and to cause periodicmeasurements of capacitance between the pair of conductors; and atransmitter for periodically transmitting capacitance and resistivemeasurements.
 13. The sensor of claim 12, wherein the electricalconductors comprise two insulated, parallel substrate conductors.